summaryrefslogtreecommitdiffstats
path: root/src/calendar.c
blob: 94dd87026c20ea9e92451a114020d7f390ed2a84 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
/*	$calcurse: calendar.c,v 1.17 2008/08/10 09:24:46 culot Exp $	*/

/*
 * Calcurse - text-based organizer
 * Copyright (c) 2004-2008 Frederic Culot
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Send your feedback or comments to : calcurse@culot.org
 * Calcurse home page : http://culot.org/calcurse
 *
 */

#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <time.h>
#include <math.h>

#include "i18n.h"
#include "day.h"
#include "apoint.h"
#include "event.h"
#include "calendar.h"
#include "custom.h"
#include "vars.h"
#include "utils.h"

#ifndef M_PI
#define	M_PI	  3.14159265358979323846
#endif

#define	EPOCH	  90
#define	EPSILONg  279.403303	/* solar ecliptic long at EPOCH */
#define	RHOg	  282.768422	/* solar ecliptic long of perigee at EPOCH */
#define	ECCEN	  0.016713	/* solar orbit eccentricity */
#define	lzero	  318.351648	/* lunar mean long at EPOCH */
#define	Pzero	  36.340410	/* lunar mean long of perigee at EPOCH */
#define	Nzero	  318.510107	/* lunar mean long of node at EPOCH */
#define TM_YEAR_BASE	1900

#define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)

static date_t today, slctd_day;
static bool week_begins_on_monday;
static pthread_mutex_t date_thread_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_t calendar_t_date;


/* Thread needed to update current date in calendar. */
static void *
calendar_date_thread (void *arg)
{
  time_t now, tomorrow;

  for (;;)
    {
      tomorrow = (time_t) (get_today () + DAYINSEC);

      while ((now = time (NULL)) < tomorrow)
	{
	  sleep (tomorrow - now);
	}

      calendar_set_current_date ();
      calendar_update_panel (win[CAL].p);
    }

  pthread_exit ((void *) 0);
}

/* Launch the calendar date thread. */
void
calendar_start_date_thread (void)
{
  pthread_create (&calendar_t_date, NULL, calendar_date_thread, NULL);
  return;
}

/* Stop the calendar date thread. */
void
calendar_stop_date_thread (void)
{
  pthread_cancel (calendar_t_date);
  return;
}

/* Set static variable today to current date */
void
calendar_set_current_date (void)
{
  time_t timer;
  struct tm *tm;

  timer = time (NULL);
  tm = localtime (&timer);

  pthread_mutex_lock (&date_thread_mutex);
  today.dd = tm->tm_mday;
  today.mm = tm->tm_mon + 1;
  today.yyyy = tm->tm_year + 1900;
  pthread_mutex_unlock (&date_thread_mutex);
}

/* Needed to display sunday or monday as the first day of week in calendar. */
void
calendar_set_first_day_of_week (wday_e first_day)
{
  switch (first_day)
    {
    case SUNDAY:
      week_begins_on_monday = false;
      break;
    case MONDAY:
      week_begins_on_monday = true;
      break;
    default:
      fputs (_("ERROR in calendar_set_first_day_of_week\n"), stderr);
      week_begins_on_monday = false;
      /* NOTREACHED */
    }
}

/* Swap first day of week in calendar. */
void
calendar_change_first_day_of_week (void)
{
  week_begins_on_monday = !week_begins_on_monday;
}

/* Return true if week begins on monday, false otherwise. */
bool
calendar_week_begins_on_monday (void)
{
  return (week_begins_on_monday);
}

/* Fill in the given variable with the current date. */
void
calendar_store_current_date (date_t *date)
{
  pthread_mutex_lock (&date_thread_mutex);
  *date = today;
  pthread_mutex_unlock (&date_thread_mutex);
}

/* This is to start at the current date in calendar. */
void
calendar_init_slctd_day (void)
{
  calendar_store_current_date (&slctd_day);
}

/* Return the selected day in calendar */
date_t *
calendar_get_slctd_day (void)
{
  return (&slctd_day);
}

/* Returned value represents the selected day in calendar (in seconds) */
long
calendar_get_slctd_day_sec (void)
{
  return (date2sec (slctd_day, 0, 0));
}

static int
isBissextile (unsigned year)
{
  return (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0));
}

static unsigned
months_to_days (unsigned month)
{
  return ((month * 3057 - 3007) / 100);
}


static long
years_to_days (unsigned year)
{
  return (year * 365L + year / 4 - year / 100 + year / 400);
}

static long
ymd_to_scalar (unsigned year, unsigned month, unsigned day)
{
  long scalar;

  scalar = day + months_to_days (month);
  if (month > 2)
    scalar -= isBissextile (year) ? 1 : 2;
  year--;
  scalar += years_to_days (year);

  return (scalar);
}

/* Function used to display the calendar panel. */
void
calendar_update_panel (WINDOW *cwin)
{
  date_t current_day, check_day;
  int c_day, c_day_1, day_1_sav, numdays, j;
  unsigned yr, mo;
  int ofs_x, ofs_y;
  int item_this_day = 0;
  int title_lines = 3;
  int sunday_first = 0;

  /* inits */
  calendar_store_current_date (&current_day);
  erase_window_part (cwin, 1, title_lines, CALWIDTH - 2, CALHEIGHT - 2);
  mo = slctd_day.mm;
  yr = slctd_day.yyyy;
  if (!calendar_week_begins_on_monday ())
    sunday_first = 1;

  /* offset for centering calendar in window */
  ofs_y = 2 + (CALHEIGHT - 9) / 2;
  ofs_x = (CALWIDTH - 27) / 2;

  /* checking the number of days in february */
  numdays = days[mo - 1];
  if (2 == mo && isBissextile (yr))
    ++numdays;

  /*
   * the first calendar day will be monday or sunday, depending on
   * 'week_begins_on_monday' value
   */
  c_day_1 = (int) ((ymd_to_scalar (yr, mo, 1 + sunday_first) - (long) 1) % 7L);

  /* Write the current month and year on top of the calendar */
  custom_apply_attr (cwin, ATTR_HIGH);
  mvwprintw (cwin, ofs_y, (CALWIDTH - (strlen (_(monthnames[mo - 1])) + 5)) / 2,
	     "%s %d", _(monthnames[mo - 1]), slctd_day.yyyy);
  custom_remove_attr (cwin, ATTR_HIGH);
  ++ofs_y;

  /* print the days, with regards to the first day of the week */
  custom_apply_attr (cwin, ATTR_HIGH);
  for (j = 0; j < 7; j++)
    {
      mvwprintw (cwin, ofs_y, ofs_x + 4 * j, "%s",
		 _(daynames[1 + j - sunday_first]));
    }
  custom_remove_attr (cwin, ATTR_HIGH);

  day_1_sav = (c_day_1 + 1) * 3 + c_day_1 - 7;

  for (c_day = 1; c_day <= numdays; ++c_day, ++c_day_1, c_day_1 %= 7)
    {
      check_day.dd = c_day;
      check_day.mm = slctd_day.mm;
      check_day.yyyy = slctd_day.yyyy;

      /* check if the day contains an event or an appointment */
      item_this_day = day_check_if_item (check_day);

      /* Go to next line, the week is over. */
      if (!c_day_1 && 1 != c_day)
	{
	  ++ofs_y;
	  ofs_x = 2 - day_1_sav - 4 * c_day - 1;
	}

      /* This is today, so print it in yellow. */
      if (c_day == current_day.dd && current_day.mm == slctd_day.mm
	  && current_day.yyyy == slctd_day.yyyy
	  && current_day.dd != slctd_day.dd)
	{
	  custom_apply_attr (cwin, ATTR_LOWEST);
	  mvwprintw (cwin, ofs_y + 1,
		     ofs_x + day_1_sav + 4 * c_day + 1, "%2d", c_day);
	  custom_remove_attr (cwin, ATTR_LOWEST);
	}
      else if (c_day == slctd_day.dd &&
	       ((current_day.dd != slctd_day.dd)
		|| (current_day.mm != slctd_day.mm)
		|| (current_day.yyyy != slctd_day.yyyy)))
	{
	  /* This is the selected day, print it in red. */
	  custom_apply_attr (cwin, ATTR_MIDDLE);
	  mvwprintw (cwin, ofs_y + 1, ofs_x + day_1_sav + 4 * c_day + 1, "%2d",
                     c_day);
	  custom_remove_attr (cwin, ATTR_MIDDLE);
	}
      else if (c_day == slctd_day.dd && current_day.dd == slctd_day.dd
	       && current_day.mm == slctd_day.mm
	       && current_day.yyyy == slctd_day.yyyy)
	{
	  /* today is the selected day */
	  custom_apply_attr (cwin, ATTR_MIDDLE);
	  mvwprintw (cwin, ofs_y + 1, ofs_x + day_1_sav + 4 * c_day + 1, "%2d",
                     c_day);
	  custom_remove_attr (cwin, ATTR_MIDDLE);
	}
      else if (item_this_day)
	{
	  custom_apply_attr (cwin, ATTR_LOW);
	  mvwprintw (cwin, ofs_y + 1, ofs_x + day_1_sav + 4 * c_day + 1, "%2d",
                     c_day);
	  custom_remove_attr (cwin, ATTR_LOW);
	}
      else
	/* otherwise, print normal days in black */
	mvwprintw (cwin, ofs_y + 1, ofs_x + day_1_sav + 4 * c_day + 1, "%2d",
                   c_day);
    }
  wnoutrefresh (cwin);
}

/* Set the selected day in calendar to current day. */
void
calendar_goto_today (void)
{
  date_t today;

  calendar_store_current_date (&today);
  slctd_day.dd = today.dd;
  slctd_day.mm = today.mm;
  slctd_day.yyyy = today.yyyy;
}

/* 
 * Ask for a date to jump to, then check the correctness of that date
 * and jump to it.
 * If the entered date is empty, automatically jump to the current date.
 * slctd_day is updated with the newly selected date.
 */
void
calendar_change_day (int datefmt)
{
#define LDAY 11
  char selected_day[LDAY] = "";
  char outstr[BUFSIZ];
  int dday, dmonth, dyear;
  int wrong_day = 1;
  char *mesg_line1 =
    _("The day you entered is not valid "
      "(should be between 01/01/1902 and 12/31/2037)");
  char *mesg_line2 = _("Press [ENTER] to continue");
  char *request_date = "Enter the day to go to [ENTER for today] : %s";

  while (wrong_day)
    {
      snprintf (outstr, BUFSIZ, request_date, DATEFMT_DESC (datefmt));
      status_mesg (_(outstr), "");
      if (getstring (win[STA].p, selected_day, LDAY, 0, 1) == GETSTRING_ESC)
	return;
      else
	{
	  if (strlen (selected_day) == 0)
	    {
	      wrong_day = 0;
              calendar_goto_today ();
	    }
	  else if (strlen (selected_day) != LDAY - 1)
	    {
	      wrong_day = 1;
	    }
	  else if (parse_date (selected_day, datefmt, &dyear, &dmonth, &dday))
	    {
	      wrong_day = 0;
	      /* go to chosen day */
	      slctd_day.dd = dday;
	      slctd_day.mm = dmonth;
	      slctd_day.yyyy = dyear;
	    }
	  if (wrong_day)
	    {
	      status_mesg (mesg_line1, mesg_line2);
	      wgetch (win[STA].p);
	    }
	}
    }

  return;
}

/* 
 * Used to change date by adding a certain amount of days or weeks.
 * Returns 0 on success, 1 otherwise.
 */
static int
date_change (struct tm *date, int delta_month, int delta_day)
{
  struct tm t;

  t = *date;
  t.tm_mon += delta_month;
  t.tm_mday += delta_day;

  if (mktime (&t) == -1)
    return (1);
  else
    {
      *date = t;
      return (0);
    }
}

void
calendar_move (move_t move)
{
  int ret, days_to_remove, days_to_add;
  struct tm t;

  memset (&t, 0, sizeof (struct tm));
  t.tm_mday = slctd_day.dd;
  t.tm_mon = slctd_day.mm - 1;
  t.tm_year = slctd_day.yyyy - 1900;

  ret =  1;
  switch (move)
    {
    case UP:
      if ((slctd_day.dd <= 7) && (slctd_day.mm == 1)
          && (slctd_day.yyyy == 1902))
	return;
      ret = date_change (&t, 0, -WEEKINDAYS);
      break;
    case DOWN:
      if ((slctd_day.dd > days[slctd_day.mm - 1] - 7)
	  && (slctd_day.mm == 12) && (slctd_day.yyyy == 2037))
	return;
      ret = date_change (&t, 0, WEEKINDAYS);
      break;
    case LEFT:
      if ((slctd_day.dd == 1) && (slctd_day.mm == 1)
	  && (slctd_day.yyyy == 1902))
	return;
      ret = date_change (&t, 0, -1);
      break;
    case RIGHT:
      if ((slctd_day.dd == 31) && (slctd_day.mm == 12)
	  && (slctd_day.yyyy == 2037))
	return;
      ret = date_change (&t, 0, 1);
      break;
    case WEEK_START:
      /* Normalize struct tm to get week day number. */
      mktime (&t);
      if (calendar_week_begins_on_monday ())
        days_to_remove = ((t.tm_wday == 0) ? WEEKINDAYS - 1 : t.tm_wday - 1);
      else
        days_to_remove = ((t.tm_wday == 0) ? 0 : t.tm_wday);
      ret = date_change (&t, 0, 0 - days_to_remove);
      break;
    case WEEK_END:
      mktime (&t);
      if (calendar_week_begins_on_monday ())
        days_to_add = ((t.tm_wday == 0) ? 0 : WEEKINDAYS - t.tm_wday);
      else
          days_to_add = ((t.tm_wday == 0) ?
                         WEEKINDAYS - 1 : WEEKINDAYS - 1 - t.tm_wday);
      ret = date_change (&t, 0, days_to_add);
      break;
    default:
      ret = 1;
      /* NOTREACHED */
    }
  if (ret == 0)
    {
      slctd_day.dd = t.tm_mday;
      slctd_day.mm = t.tm_mon + 1;
      slctd_day.yyyy = t.tm_year + 1900;
    }
}

/* Returns the beginning of current year as a long. */
long
calendar_start_of_year (void)
{
  time_t timer;
  struct tm *tm;

  timer = time (NULL);
  tm = localtime (&timer);
  tm->tm_mon = 0;
  tm->tm_mday = 1;
  tm->tm_hour = 0;
  tm->tm_min = 0;
  tm->tm_sec = 0;
  timer = mktime (tm);

  return (long)timer;
}

long
calendar_end_of_year (void)
{
  time_t timer;
  struct tm *tm;

  timer = time (NULL);
  tm = localtime (&timer);
  tm->tm_mon = 0;
  tm->tm_mday = 1;
  tm->tm_hour = 0;
  tm->tm_min = 0;
  tm->tm_sec = 0;
  tm->tm_year++;
  timer = mktime (tm);

  return (long)(timer - 1);
}

/*
 * The pom, potm, dotr, adj360 are used to compute the current 
 * phase of the moon.
 * The code is based on the OpenBSD version of pom(6).
 * Below is reported the copyright notice.
 */
/*
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software posted to USENET.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * dtor --
 *	convert degrees to radians
 */
static double
dtor (double deg)
{
  return (deg * M_PI / 180);
}

/*
 * adj360 --
 *	adjust value so 0 <= deg <= 360
 */
static void
adj360 (double *deg)
{
  for (;;)
    if (*deg < 0.0)
      *deg += 360.0;
    else if (*deg > 360.0)
      *deg -= 360.0;
    else
      break;
}

/*
 * potm --
 *	return phase of the moon
 */
static double
potm (double days)
{
  double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
  double A4, lprime, V, ldprime, D, Nm;

  N = 360.0 * days / 365.242191;	/* sec 46 #3 */
  adj360 (&N);
  Msol = N + EPSILONg - RHOg;	/* sec 46 #4 */
  adj360 (&Msol);
  Ec = 360 / M_PI * ECCEN * sin (dtor (Msol));	/* sec 46 #5 */
  LambdaSol = N + Ec + EPSILONg;	/* sec 46 #6 */
  adj360 (&LambdaSol);
  l = 13.1763966 * days + lzero;	/* sec 65 #4 */
  adj360 (&l);
  Mm = l - (0.1114041 * days) - Pzero;	/* sec 65 #5 */
  adj360 (&Mm);
  Nm = Nzero - (0.0529539 * days);	/* sec 65 #6 */
  adj360 (&Nm);
  Ev = 1.2739 * sin (dtor (2 * (l - LambdaSol) - Mm));	/* sec 65 #7 */
  Ac = 0.1858 * sin (dtor (Msol));	/* sec 65 #8 */
  A3 = 0.37 * sin (dtor (Msol));
  Mmprime = Mm + Ev - Ac - A3;	/* sec 65 #9 */
  Ec = 6.2886 * sin (dtor (Mmprime));	/* sec 65 #10 */
  A4 = 0.214 * sin (dtor (2 * Mmprime));	/* sec 65 #11 */
  lprime = l + Ev + Ec - Ac + A4;	/* sec 65 #12 */
  V = 0.6583 * sin (dtor (2 * (lprime - LambdaSol)));	/* sec 65 #13 */
  ldprime = lprime + V;		/* sec 65 #14 */
  D = ldprime - LambdaSol;	/* sec 67 #2 */
  return (50.0 * (1 - cos (dtor (D))));	/* sec 67 #3 */
}

/*
 * Phase of the Moon.  Calculates the current phase of the moon.
 * Based on routines from `Practical Astronomy with Your Calculator',
 * by Duffett-Smith.  Comments give the section from the book that
 * particular piece of code was adapted from.
 *
 * -- Keith E. Brandt  VIII 1984
 *
 * Updated to the Third Edition of Duffett-Smith's book, IX 1998
 *
 */
static double
pom (time_t tmpt)
{
  struct tm *GMT;
  double days;
  int cnt;
  pom_e pom;

  pom = NO_POM;
  GMT = gmtime (&tmpt);
  days = (GMT->tm_yday + 1) + ((GMT->tm_hour + (GMT->tm_min / 60.0) +
				(GMT->tm_sec / 3600.0)) / 24.0);
  for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt)
    days += isleap (cnt + TM_YEAR_BASE) ? 366 : 365;
  /* Selected time could be before EPOCH */
  for (cnt = GMT->tm_year; cnt < EPOCH; ++cnt)
    days -= isleap (cnt + TM_YEAR_BASE) ? 366 : 365;

  return (potm (days));
}

/*
 * Return a pictogram representing the current phase of the moon.
 * Careful: date is the selected day in calendar at 00:00, so it represents
 * the phase of the moon for previous day.
 */
char *
calendar_get_pom (time_t date)
{
  char *pom_pict[MOON_PHASES] = { "   ", "|) ", "(|)", "(| ", " | " };
  pom_e phase = NO_POM;
  double pom_today, relative_pom, pom_yesterday, pom_tomorrow;
  const double half = 50.0;

  pom_yesterday = pom (date);
  pom_today = pom (date + DAYINSEC);
  relative_pom = abs (pom_today - half);
  pom_tomorrow = pom (date + 2 * DAYINSEC);
  if (pom_today > pom_yesterday && pom_today > pom_tomorrow)
    phase = FULL_MOON;
  else if (pom_today < pom_yesterday && pom_today < pom_tomorrow)
    phase = NEW_MOON;
  else if (relative_pom < abs (pom_yesterday - half)
           && relative_pom < abs (pom_tomorrow - half))
    phase = (pom_tomorrow > pom_today) ? FIRST_QUARTER : LAST_QUARTER;

  return (pom_pict[phase]);
}